The present invention relates to a wheel body for carriages or other vehicles which are used, inter alia, in roller-coasters and other installations of amusement parks.
According to the prior art, wheels or wheel bodies for carriages or other vehicles used, inter alia, in roller-coasters and other installations of amusement parks, are fabricated from an aluminum alloy. Because of the good castability of the latter, Al-Si alloys are often used for this application. Carriages or other vehicles used in the roller-coasters and other installations of amusement parks comprises not only wheels for forward movement of the vehicle on the installation, but also wheels by which the vehicle in the installation bears against a guide.
These guide wheels do not make continuous contact with the guide, instead the contact between the guide wheel and the guide is subject to interruptions. When the contact between a guide wheel and the guide is broken, the speed of rotation of the wheel will decrease. When the contact between the guide wheel and the guide is subsequently restored, the guide wheel will be subject to large acceleration. In order to be able to sustain the acceleration and the changing stresses which occur when the contact between the guide wheel and the guide is broken and restored, a guide wheel is ideally made from a ductile material. In order, moreover, to be able to absorb more effectively the shock which occurs when the wheel makes contact with the guide, the running tread of the wheels is preferably provided with a running tread of plastic. A second effect of such a plastic running tread being fitted is that noise is reduced. In the prior art it is customary to provide the wheels used in roller-coasters and comparable installations with a running tread of polyurethane rubber, fixed in an exothermal reaction in a vulcanization process. In that exothermal reaction the temperature may increase to up to 160.degree. C.
A first important drawback of the wheels which are used in roller-coasters and comparable installations according to the prior art is that the Al-Si alloys used have relatively low elongation at rupture, less than 10%. Because of the enormous mechanical stresses to which the wheels are subjected, there is a risk that the wheels may break spontaneously without much deformation during overloading or after having been damaged. Certainly, given that the roller-coasters and comparable installations are most commonly used in an environment where many people are present, this means that life-endangering situations can thus be created.
A second important drawback of the wheels which are used in roller-coasters and comparable installations according to the prior art is that the mechanical characteristics of the Al-Si alloys used are adversely affected under the influence of thermal stress in the region of 160.degree. C. This means that each time a running tread of polyurethane is applied to the wheel by means of an exothermal reaction in the vulcanization process, the mechanical characteristics of the wheel will change. In the prior art the maximum number of times a wheel is allowed to be provided with a new running tread of polyurethane rubber is therefore restricted to a limited number of times, for example five times.